U.S. patent application number 11/051192 was filed with the patent office on 2005-09-01 for power source apparatus and vehicular lamp.
This patent application is currently assigned to KOITO MANUFACTURING CO., LTD.. Invention is credited to Ito, Masayasu, Namba, Takanori.
Application Number | 20050189822 11/051192 |
Document ID | / |
Family ID | 34836098 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050189822 |
Kind Code |
A1 |
Namba, Takanori ; et
al. |
September 1, 2005 |
Power source apparatus and vehicular lamp
Abstract
There is provided a vehicular lamp at low cost. A power source
apparatus includes: an output controlling switch operable to
intermittently carry an electric current; an output coil operable
to accumulate energy according to the current flowing into the
output controlling switch and to output an electric power based on
the accumulated energy when the output controlling switch is turned
off; an end detecting unit operable to detect that the output coil
ends the output of the power; and an output controlling unit, in
which the output controlling unit includes: a time memorizing unit
that memorizes OFF time for which the output controlling switch
should be kept off; a switch controlling unit that switches the
output controlling switch on and off based on the OFF time
memorized in the time memorizing unit; and a time changing unit
that changes the OFF time memorized in the time memorizing unit.
The time changing unit increases the OFF time when the end
detecting unit is not detecting the end of the output and decreases
the OFF time when the end detecting unit is detecting the end of
the output, in the timing when the output controlling switch is
turned on.
Inventors: |
Namba, Takanori; (Shizuoka,
JP) ; Ito, Masayasu; (Shizuoka-Shi, JP) |
Correspondence
Address: |
OSHA LIANG L.L.P.
1221 MCKINNEY STREET
SUITE 2800
HOUSTON
TX
77010
US
|
Assignee: |
KOITO MANUFACTURING CO.,
LTD.
Tokyo
JP
|
Family ID: |
34836098 |
Appl. No.: |
11/051192 |
Filed: |
February 4, 2005 |
Current U.S.
Class: |
307/149 |
Current CPC
Class: |
H05B 45/385 20200101;
H05B 45/3725 20200101 |
Class at
Publication: |
307/149 |
International
Class: |
G06K 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2004 |
JP |
JP2004-032635 |
Claims
What is claimed is:
1. A power source apparatus comprising: an output controlling
switch operable to intermittently carry an electric current by
repeating on and off; an output coil operable to accumulate energy
according to the current flowing into said output controlling
switch when said output controlling switch is turned on and to
output an electric power based on the accumulated energy when said
output controlling switch is turned off; an end detecting unit
operable to detect that said output coil ends the output of the
power; and an output controlling unit operable to switch said
output controlling switch on and off, wherein said output
controlling unit comprises: a time memorizing unit that memorizes
OFF time for which said output controlling switch should be kept
off; a switch controlling unit that switches said output
controlling switch on and off based on the OFF time memorized in
said time memorizing unit; and a time changing unit that changes
the OFF time memorized in said time memorizing unit, wherein said
time changing unit increases the OFF time when said end detecting
unit is not detecting the end of the output and decreases the OFF
time when said end detecting unit is detecting the end of the
output, in the timing when said output controlling switch is turned
on.
2. The power source apparatus as claimed in claim 1, wherein said
power source apparatus sequentially supplies electric power to each
of a plurality of loads connected in parallel, said time memorizing
unit memorizes the plurality of OFF time in association with each
of the plurality of loads, said output controlling unit further
comprises a selection controlling unit that sequentially selects
each of the plurality of loads, said switch controlling unit
switches said output controlling switch on and off based on the OFF
time corresponding to the load selected by said selection
controlling unit, said output coil supplies electric power to the
load selected by said selection controlling unit, and said time
changing unit changes the OFF time corresponding to the load
selected by said selection controlling unit.
3. The power source apparatus as claimed in claim 1, wherein said
time memorizing unit is a counter that memorizes numerical value
corresponding to the OFF time, said time changing unit changes the
numerical value memorized in said time memorizing unit by a
predetermined first modification value when said end detecting unit
is not detecting the end of the output in the timing when said
output controlling switch is turned on, and said time changing unit
changes the numerical value memorized in said time memorizing unit
by a predetermined second modification value in the opposite
direction from what is not detecting the end of the output when
said end detecting unit is detecting the end of the output in the
timing when said output controlling switch is turned on.
4. A vehicular lamp used for a vehicle, comprising: a light source
unit emitting light; and a power source unit supplying electric
power to said light source unit, wherein said power source unit
comprises: an output controlling switch that intermittently carries
an electric current by repeating on and off; an output coil that
accumulates energy according to the current flowing into said
output controlling switch when said output controlling switch is
turned on and outputs an electric power based on the accumulated
energy when said output controlling switch is turned off; an end
detecting unit that detects that said output coil ends the output
of the power; and an output controlling unit that is made up of a
microcomputer in at least a part thereof and switches said output
controlling switch on and off, and said output controlling unit
comprises: a time memorizing unit that memorizes OFF time for which
said output controlling switch should be kept off; a switch
controlling unit that switches said output controlling switch on
and off based on the OFF time memorized in said time memorizing
unit; and a time changing unit that changes the OFF time memorized
in said time memorizing unit, wherein said time changing unit
increases the OFF time when said end detecting unit is not
detecting the end of the output and decreases the OFF time when
said end detecting unit is detecting the end of the output, in the
timing when said output controlling switch is turned on.
Description
[0001] This patent application claims priority from a Japanese
Patent Application No. 2004-032635 filed on Feb. 9, 2004, the
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a power source apparatus
and a vehicular lamp.
[0004] 2. Description of Related Art
[0005] Conventionally, a vehicular lamp that uses a light-emitting
diode element is known as disclosed, for example, in Japanese
Patent Laid-Open No. 2002-231013. Alight-emitting diode element for
a vehicular lamp emits light according to electric power received
from, e.g. a switching regulator.
[0006] The switching regulator emits electric power energy in
synchronization with the timing in which a switching element
switches. In this case, it is preferable that the switching element
is controlled based on the end of energy emission, in some cases.
However, there was conventionally a problem that a cost of a
vehicular lamp increases due to a cost of circuitry for detecting
the end of energy emission.
SUMMARY OF THE INVENTION
[0007] Therefore, it is an object of the present invention to
provide a power source apparatus and a vehicular lamp that can
solve the foregoing problems. The above and other objects can be
achieved by combinations described in the independent claims. The
dependent claims define further advantageous and exemplary
combinations of the present invention.
[0008] According to the first aspect of the present invention,
there is provided a power source apparatus. The power source
apparatus includes: an output controlling switch operable to
intermittently carry an electric current by repeating on and off;
an output coil operable to accumulate energy according to the
current flowing into the output controlling switch when the output
controlling switch is turned on and to output an electric power
based on the accumulated energy when the output controlling switch
is turned off; an end detecting unit operable to detect that the
output coil ends the output of the power; and an output controlling
unit operable to switch the output controlling switch on and off,
in which the output controlling unit includes: a time memorizing
unit that memorizes OFF time for which the output controlling
switch should be kept off; a switch controlling unit that switches
the output controlling switch on and off based on the OFF time
memorized in the time memorizing unit; and a time changing unit
that changes the OFF time memorized in the time memorizing unit, in
which the time changing unit increases the OFF time when the end
detecting unit is not detecting the end of the output and decreases
the OFF time when the end detecting unit is detecting the end of
the output, in the timing when the output controlling switch is
turned on.
[0009] The power source apparatus may sequentially supply electric
power to each of a plurality of loads connected in parallel, the
time memorizing unit may memorize the plurality of OFF time in
association with each of the plurality of loads, the output
controlling unit may further include a selection controlling unit
that sequentially selects each of the plurality of loads, the
switch controlling unit may switch the output controlling switch on
and off based on the OFF time corresponding to the load selected by
the selection controlling unit, the output coil may supply electric
power to the load selected by the selection controlling unit, and
the time changing unit may change the OFF time corresponding to the
load selected by the selection controlling unit.
[0010] The time memorizing unit may be a counter that memorizes
numerical value corresponding to the OFF time, the time changing
unit may change the numerical value memorized in the time
memorizing unit by a predetermined first modification value when
the end detecting unit is not detecting the end of the output in
the timing when the output controlling switch is turned on, and the
time changing unit may change the numerical value memorized in the
time memorizing unit by a predetermined second modification value
in the opposite direction from what is not detecting the end of the
output when the end detecting unit is detecting the end of the
output in the timing when the output controlling switch is turned
on.
[0011] According to the second aspect of the present invention,
there is provided a vehicular lamp used for a vehicle. The
vehicular lamp includes: a light source unit emitting light; and a
power source unit supplying electric power to the light source
unit, in which the power source unit includes: an output
controlling switch that intermittently carries an electric current
by repeating on and off; an output coil that accumulates energy
according to the current flowing into the output controlling switch
when the output controlling switch is turned on and outputs an
electric power based on the accumulated energy when the output
controlling switch is turned off; an end detecting unit that
detects that the output coil ends the output of the power; and an
output controlling unit that is made up of a microcomputer in at
least a part thereof and switches the output controlling switch on
and off, and the output controlling unit includes: a time
memorizing unit that memorizes OFF time for which the output
controlling switch should be kept off; a switch controlling unit
that switches the output controlling switch on and off based on the
OFF time memorized in the time memorizing unit; and a time changing
unit that changes the OFF time memorized in the time memorizing
unit, in which the time changing unit increases the OFF time when
the end detecting unit is not detecting the end of the output and
decreases the OFF time when the end detecting unit is detecting the
end of the output, in the timing when the output controlling switch
is turned on.
[0012] The summary of the invention does not necessarily describe
all necessary features of the present invention. The present
invention may also be a sub-combination of the features described
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The above and other objects and features and advantages of
the present invention will become more apparent from the following
description of the presently preferred exemplary embodiments of the
invention taken in conjunction with the accompanying drawings, in
which:
[0014] FIG. 1 is a diagram exemplary showing a configuration of a
vehicular lamp according to an embodiment of the present
invention;
[0015] FIG. 2 is a diagram exemplary showing a configuration of an
end detecting unit;
[0016] FIGS. 3A to 3C are timing charts exemplary showing an
operation of an end detecting unit;
[0017] FIG. 4 is a flowchart exemplary showing an operation of a
vehicular lamp; and
[0018] FIG. 5 is a diagram showing another example of a
configuration of a vehicular lamp.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The invention will now be described based on the preferred
embodiments, which do not intend to limit the scope of the present
invention, but exemplify the invention. All of the features and the
combinations thereof described in the embodiment are not
necessarily essential to the invention.
[0020] FIG. 1 is a diagram exemplary showing a configuration of a
vehicular lamp 10 according to an embodiment of the present
invention along with a reference voltage power source 50. The
reference voltage power source 50 is, e.g., a battery in a vehicle
and supplies a predetermined DC voltage to the vehicular lamp 10.
In this example, the vehicular lamp 10 includes a light source unit
104 and a power source unit 100. In the vehicular lamp 10 of the
present example, it is an object to adequately control a switching
regulator 102 of the power source unit 100 at low cost.
[0021] The light source unit 104 includes one or more
light-emitting diode element 12. The light-emitting diode element
12 is an example of a semiconductor light-emitting element and
emits light according to electric power received from the power
source unit 100. Additionally, in another example, the vehicular
lamp 10 may include a plurality of light source units 104 connected
in parallel.
[0022] The power source unit 100 includes a switching regulator
102, a diode 210, a condenser 318, an end detecting unit 106, and
an output controlling unit 108. The switching regulator 102
includes an output controlling switch 312 and a transformer
306.
[0023] The output controlling switch 312 is connected with a
primary coil 402 of the transformer 306 in series, and
intermittently carries an electric current by repeating on and off
according to the control of the output controlling unit 108. In
this way, the output controlling switch 312 intermittently changes
the current flowing into the primary coil 402.
[0024] The transformer 306 has the primary coil 402 and a secondary
coil 404. When the output controlling switch 312 is turned on, the
primary coil 402 streams the current received from the reference
voltage power source 50. The secondary coil 404 is an example of an
output coil, and supplies electric power according to the current
flowing into the primary coil 402 to the light source unit 104 via
the diode 210. In this example, the secondary coil 404 accumulates
energy according to the current flowing into the output controlling
switch 312 and the primary coil 402 when the output controlling
switch 312 is turned on. Meanwhile, the secondary coil 404 outputs
electric power based on the accumulated energy when the output
controlling switch 312 is turned off. In addition, the diode 210 is
a rectification diode that is connected in a forward direction
between the secondary coil 404 and the light source unit 104. The
current flowing into the light source unit 104 is smoothed by the
condenser 318.
[0025] The end detecting unit 106 includes a secondary side
operation detecting circuit 406 and an on-timing inspecting circuit
408. The secondary side operation detecting circuit 406 identifies
whether the emission of energy by the secondary coil 404 was ended
based on a voltage of an output terminal of the secondary coil 404.
Here, it may be identified whether the emission was ended based on
a voltage of a connection point between the output controlling
switch 312 and the primary coil 402. In this way, the end detecting
unit 106 detects that the secondary coil 404 ends the output of
electric power.
[0026] The on-timing inspecting circuit 408 receives an
identification result by the secondary side operation detecting
circuit 406 from the secondary side operation detecting circuit
406, and receives a control signal for the output controlling
switch 312 from the output controlling unit 108. This control
signal is a signal to switch the output controlling switch 312 on
and off.
[0027] In addition, the on-timing inspecting circuit 408 detects an
identification result in the timing when the output controlling
switch 312 is turned on, and supplies the detected result to the
output controlling unit 108. In this way, the end detecting unit
106 informs the output controlling unit 108 of an operation mode of
the secondary coil 404 in the timing when the output controlling
switch 312 is turned on.
[0028] In this example, the end detecting unit 106 informs the
output controlling unit 108 of whether an operation of the
secondary coil 404 is either of a current discontinuous mode or a
current continuous mode. Here, a current discontinuous mode is a
mode in which the secondary coil 404 ends the output of power,
e.g., before the output controlling switch 312 is turned on. In
addition, a current continuous mode is a mode in which the
secondary coil 404 is not ending the output of power, e.g., in the
timing when the output controlling switch 312 is turned on. In this
way, the end detecting unit 106 informs the output controlling unit
108 of whether the secondary coil 404 ends the output of electric
power.
[0029] The output controlling unit 108 is made up of a
microcomputer, and includes a time memorizing unit 412, a switch
controlling unit 410, and a time changing unit 414. The time
memorizing unit 412 memorizes OFF time for which the output
controlling switch 312 should be kept off. In this example, the
time memorizing unit 412 is a counter that memorizes numerical
value corresponding to the OFF time.
[0030] The switch controlling unit 410 supplies a control signal
based on the OFF time memorized in the time memorizing unit 412 to
the output controlling switch 312 to control the output controlling
switch 312. In this way, for example, when the output controlling
switch 312 is turned off, the switch controlling unit 410 keeps the
output controlling switch 312 off for the OFF time. Additionally,
in this example, the switch controlling unit 410 computes ON time
for which the output controlling switch 312 should be kept on based
on an output voltage of the power source unit 100 or the switching
regulator 102. In this example, the output controlling switch 312
memorizes numerical value corresponding to the ON time, e.g., with
a counter. Then, when turning on the output controlling switch 312
next, the switch controlling unit 410 keeps the output controlling
switch 312 on for the computed ON time. In this way, the output
controlling unit 108 switches the output controlling switch 312 on
and off based on the computed ON time and the OFF time memorized in
the time memorizing unit 412.
[0031] In addition, in another example, the output controlling unit
108 may compute ON time based on an electric current flowing into
the light source unit 104. In this case, the light source unit 104
further has, e.g., a resistor connected with the light source unit
104 in series. Thus, the output controlling unit 108 detects an
electric current flowing into the light source unit 104 based on
voltage of both ends of this resistor.
[0032] The time changing unit 414 changes the OFF time memorized in
the time memorizing unit 412 according to information from the end
detecting unit 106. For example, when receiving information that an
operation of the secondary coil 404 is a current continuous mode
from the end detecting unit 106, the time changing unit 414
increases the OFF time. In addition, when receiving information
that an operation of the secondary coil 404 is a current
discontinuous mode, the time changing unit 414 decreases the OFF
time. In this way, when the end detecting unit 106 is not detecting
the end of output in the timing when the output controlling switch
312 is turned on, the time changing unit 414 increases the OFF
time. Further, when the end detecting unit 106 is detecting the end
of output, the time changing unit 414 decreases the OFF time.
[0033] Therefore, according to this example, the switching
regulator 102 can adequately be operated in a current boundary
mode. Here, a current boundary mode is an operation mode in which
the output controlling switch 312 is turned on when the secondary
coil 404 has completely emitted energy. In this way, the switching
regulator 102 can be operated efficiently.
[0034] In addition, according to this example, it is possible to
adequately control the output controlling switch 312 using the
output controlling unit 108 that is made up of a cheap
microcomputer, e.g., without a high-speed interrupt handling
function. Therefore, according to this example, the vehicular lamp
10 can be offered at low cost.
[0035] Additionally, in another example, e.g., a part of the end
detecting unit 106 may be made up of a microcomputer along with the
output controlling unit 108. For example, a part of the output
controlling unit 108 may also be made up of a microcomputer. In
these cases, the switching regulator 102 can adequately be operated
in a current boundary mode using a cheap microcomputer.
[0036] FIG. 2 is a diagram exemplary showing a configuration of the
end detecting unit 106. In this example, the secondary side
operation detecting circuit 406 of the end detecting unit 106
includes a plurality of resistors 702 and 704, a plurality of
diodes 706 and 708, and a Schmidt trigger inverter 710.
[0037] The plurality of resistors 702 and 704 divides the voltage
V.sub.out of the output terminal of the secondary coil 404, and
supply it to the Schmidt trigger inverter 710. The diode 706 is
connected between an input terminal of the Schmidt trigger inverter
710 and a predetermined power source voltage V.sub.cc in the
reverse direction. In addition, the diode 708 connected between the
input terminal of the Schmidt trigger inverter 710 and a
predetermined ground potential in the reverse direction. In this
way, the plurality of diodes 706 and 708 protects the input
terminal of the Schmidt trigger inverter 710.
[0038] The Schmidt trigger inverter 710 supplies the comparison
result between the plurality of resistors 702 and 704 and a
predetermined threshold voltage to the on-timing inspecting circuit
408. In this way, the secondary side operation detecting circuit
406 detects that the secondary coil 404 ends the output of electric
power. In this example, when the secondary coil 404 ends the output
of electric power, the secondary side operation detecting circuit
406 outputs an H signal to the on-timing inspecting circuit 408
according to voltage reduction of the output terminal of the
secondary coil 404. In addition, when the secondary coil 404 is not
ending the output of electric power, the secondary side operation
detecting circuit 406 outputs an L signal. According to this
example, it is possible to detect the end of power output with high
precision by using the Schmidt trigger inverter 710 having a low
threshold voltage.
[0039] The on-timing inspecting circuit 408 includes a plurality of
Schmidt trigger inverters 716a to 716c and a plurality of
flip-flops 712 and 714. The plurality of Schmidt trigger inverters
716a to 716c is serially connected. The Schmidt trigger inverter
716a in a first stage receives a control signal for the output
controlling switch 312 (see FIG. 1) from the switch controlling
unit 410. In this way, the Schmidt trigger inverter 716b in a next
stage outputs a normal signal V.sub.2 of the control signal, and
the Schmidt trigger inverter 716c in a last stage outputs an
inversion signal V.sub.3 of the control signal.
[0040] The plurality of flip-flops 712 and 714 is D flip-flops. The
flip-flop 712 receives an output V.sub.1 of the Schmidt trigger
inverter 710 through a clock terminal CK and the inversion signal
V.sub.3 of the control signal through a /CLR terminal (a CLR bar
terminal). In addition, a D input terminal and a /PR terminal (a PR
bar signal terminal) of the flip-flop 712 receive a power source
voltage Vcc. Here, the Schmidt trigger inverters 716a to 716c may
be a mere inverter.
[0041] In this case, when an input V.sub.1 rises while the
inversion signal V.sub.3 is H, the flip-flop 712 outputs an H
signal. Here, the inversion signal V.sub.3 becomes H when the
output controlling switch 312 is off. In addition, the input
V.sub.1 rises when the secondary coil 404 ends the output of
electric power. For that purpose, in this example, the flip-flop
712 outputs an H signal when the secondary coil 404 ends the output
of electric power while the output controlling switch 312 is in
off.
[0042] The flip-flop 714 receives the normal signal V.sub.2 of the
control signal through a clock terminal CK and a Q output V.sub.4
of the flip-flop 712 through a D input terminal. A /CLR terminal
and /PR terminal of the flip-flop 714 receives the power source
voltage V.sub.cc. In addition, the flip-flop 714 supplies a Q
output V.sub.5 to the time changing unit 414.
[0043] In this case, the flip-flop 712 supplies the Q output
V.sub.4 of the flip-flop 712 to the time changing unit 414 in
response to a rising edge of the normal signal V.sub.2. Here, the
normal signal V.sub.2 becomes H when the output controlling switch
312 is on. Therefore, the flip-flop 714 supplies the Q output
V.sub.4 of the flip-flop 712 in the timing when the output
controlling switch 312 is turned on to the time changing unit
414.
[0044] Therefore, when the secondary coil 404 ends the output of
electric power while the output controlling switch 312 is in off
just before on, the flip-flop 714 outputs an H signal as the Q
output V.sub.5. In this way, the on-timing inspecting circuit 408
informs the time changing unit 414 of the information that an
operation of the switching regulator 102 (see FIG. 1) is a current
discontinuous mode. For example, when the voltage of the output
terminal of the secondary coil 404 is substantially 0V in the
timing when the output controlling switch 312 is turned on, the
on-timing inspecting circuit 408 informs the time changing unit 414
of a current discontinuous mode.
[0045] In addition, when the secondary coil 404 is not ending the
output of electric power while the output controlling switch 312 is
in off just before on, the flip-flop 714 outputs an L signal as the
Q output V.sub.5. In this way, the on-timing inspecting circuit 408
informs the time changing unit 414 of the information that an
operation of the switching regulator 102 is a current continuous
mode. According to this example, it is possible to detect an
operation mode of the switching regulator 102 adequately.
[0046] Here, in another example, a voltage of the output terminal
of the secondary coil 404 may also be detected by, e.g., an
interrupt of a microcomputer. However, in this case, since the
vehicular lamp 10 has to perform voltage detection with precision
not more than, e.g., about 500 ns, there can be required a
high-speed microcomputer not less than, e.g., about 120 MHz in some
cases when considering interrupt delay (for example, about 60
clocks in 30 states having two clocks per one state). However, the
cost of vehicular lamp 10 increases due to such a high-speed
microcomputer.
[0047] Additionally, it is conceivable that the output controlling
unit 108 (see FIG. 1) is made up of a dedicated PWM (pulse-width
modulation) controlling circuit without the use of a microcomputer.
However, the PWM controlling circuit is large-scale circuitry
because it includes a comparator and an Op-Amp or a dedicated
PWMIC. Therefore, in this case, the cost of vehicular lamp 10 also
increases.
[0048] However, in this example, the end detecting unit 106 detects
whether an operation of the secondary coil 404 is a current
discontinuous mode or a current continuous mode using the secondary
side operation detecting circuit 406 and the on-timing inspecting
circuit 408 that can be composed by cheap circuit elements. Then,
the output controlling unit 108 changes OFF time in the control
signal based on a detection result of the end detecting unit 106.
Therefore, according to this example, since a high-speed interrupt
is not required, the output control region 108 can be made up of a
cheap microcomputer. In this way, it is also possible to provide
the vehicular lamp 10 at low cost. Further, the vehicular lamp 10
can be miniaturized by composing the output controlling unit 108
with a microcomputer.
[0049] In addition, this microcomputer may be a microcomputer that
is used in common with the other control unit in the vehicle. For
example, this microcomputer may further control a swivel and an
automatic leveling of an Adaptive Frontlighting System. In this
way, the number of components in the control unit of the vehicle
can be reduced.
[0050] FIGS. 3A to 3C are timing charts exemplary showing an
operation of the end detecting unit 106. FIG. 3A shows an operation
of the end detecting unit 106 in case of a current continuous mode.
In this case, since the output controlling switch 312 is turned on
while the secondary coil 404 outputs electric power, the normal
signal V.sub.2 of the control signal rises up while the output
V.sub.1 of the Schmidt trigger inverter 710 is L. Therefore, the
flip-flops 712 and 714 output the L signal as the Q outputs V4 and
V5.
[0051] FIG. 3B shows an operation of the end detecting unit 106 in
case of a current discontinuous mode. In this case, since the
output controlling switch 312 is turned on after the secondary coil
404 ends the output of electric power, the normal signal V.sub.2 of
the control signal rises up after the output V.sub.1 of the Schmidt
trigger inverter 710 is inverted into H. Therefore, the flip-flop
712 outputs a pulse signal in response to rising of the output
V.sub.1 as the Q output V.sub.4. Then, the flip-flop 714 outputs
the H signal in response to rising of the normal signal V.sub.2
based on this pulse signal.
[0052] FIG. 3C shows an operation of the end detecting unit 106
when resonance is generated in the output terminal of the secondary
coil 404 in a current discontinuous mode. When resonance is
generated in the output terminal of the secondary coil 404, the
output V.sub.1 of the Schmidt trigger inverter 710 resonates in
accordance with this resonance. However, the Q output V.sub.4 of
the flip-flop 712 is cleared in the timing when the output
controlling switch 312 is turned on. For that purpose, after the
flip-flop 714 latches the D input in synchronization with the
timing when the output controlling switch 312 is turned on, the
flip-flop 714 holds the value of the Q output V.sub.5 while the
output controlling switch 312 is turned from off to on. In this
case, although resonance is generated in a current or a voltage of
the output terminal of the secondary coil 404, e.g., after the
secondary coil 404 ends the output of electric power, the resonance
can adequately be distinguished from voltage fluctuation by an
operation of the secondary coil 404. Therefore, according to this
example, an operation mode of the switching regulator 102 can be
detected adequately.
[0053] FIG. 4 is a flowchart exemplary showing an operation of the
vehicular lamp 10. In this example, the switch controlling unit 410
first sets the default value of a target voltage V.sub.set as
opposed to the output voltage of the secondary coil 404, and ON
time T.sub.on and OFF time T.sub.off in the control signal (S102).
In this case, the default value of the OFF time T.sub.off is
memorized in the time memorizing unit 412.
[0054] Then, the switch controlling unit 410 outputs a pulse of the
control signal based on the set ON time T.sub.on and OFF time
T.sub.off (S104), and reads an output voltage V.sub.r output from
the power source unit 100 or the switching regulator 102
(S106).
[0055] Here, when the output voltage V.sub.r is higher than the
target voltage V.sub.set (S108: Yes), the switch controlling unit
410 decreases the ON time T.sub.on by decrementing numerical value
corresponding to the ON time Ton by one (S110). In this way, energy
accumulated in the secondary coil 404 is decreased according to a
pulse of the control signal, and thus the output voltage of the
secondary coil 404 is decreased.
[0056] In addition, when the output voltage V.sub.r is lower than
the target voltage V.sub.set (S108: No), the switch controlling
unit 410 increases the ON time T.sub.on by incrementing numerical
value corresponding to the ON time T.sub.on by one (S112). In this
way, energy accumulated in the secondary coil 404 is increased
according to a pulse of the control signal, and thus the output
voltage of the secondary coil 404 is increased. For that purpose,
according to this example, the output voltage of the switching
regulator 102 can adequately be controlled in accordance with the
target voltage V.sub.set.
[0057] Next, the end detecting unit 106 detects whether an
operation of the switching regulator 102 is a current continuous
mode (S114). When it is a current continuous mode (S114: Yes), the
time changing unit 414 increments the numerical value corresponding
to the OFF time T.sub.off in the time memorizing unit 412 by one
(S116). In this way, the time changing unit 414 increases the OFF
time T.sub.off to delay the timing when the output controlling
switch 312 is turned on. In addition, the time changing unit 414
brings an operation of the switching regulator 102 close to a
current boundary mode.
[0058] In addition, when an operation of the switching regulator
102 is not a current continuous mode (S114: No), the time changing
unit 414 decrements the numerical value corresponding to the OFF
time T.sub.off by one (S118). In this way, the time changing unit
414 decreases the OFF time T.sub.off to hasten the timing when the
output controlling switch 312 is turned on. In this case, the time
changing unit 414 also brings an operation of the switching
regulator 102 close to a current boundary mode. For that purpose,
according to this example, the switching regulator 102 can
adequately be operated in a current boundary mode.
[0059] Then, the switch controlling unit 410 sets new ON time
T.sub.on and OFF time T.sub.off changed (S120), and then returns to
the S104 to output a pulse of the next control signal (S104).
According to this example, the switching regulator 102 can be
controlled adequately.
[0060] In addition, in the S110 or S112, the switch controlling
unit 410 may change the ON time T.sub.on by a predetermined value
aside from one. Further, in the S116 or S118, the time changing
unit 414 may change the OFF time T.sub.off by a predetermined value
aside from one. For example, when the end detecting unit 106 is not
detecting the end of output in the timing when the output
controlling switch 312 is turned on, the time changing unit 414 may
change the numerical value stored on the time memorizing unit 412
by the first predetermined modification value. In addition, when
the end detecting unit 106 is detecting the end of output in the
timing when the output controlling switch 312 is turned on, the
time changing unit 414 may change the numerical value stored on the
time memorizing unit 412 by the second predetermined modification
value in the opposite direction from what is not detecting the end
of the output.
[0061] FIG. 5 is a diagram showing another example of a
configuration of a vehicular lamp 10. In addition, the explanation
of the configuration of FIG. 5 having the same reference number as
FIG. 1 will be omitted except the components that are below
explained because the configuration of the same reference number
has the same or similar function. In this example, the vehicular
lamp 10 includes a plurality of light source units 104a and 104b
connected in parallel. The light source units 104 are an example of
a load connected to a power source unit 100.
[0062] The power source unit 100 includes a plurality of diodes
210a and 210b and a plurality of condensers 318a and 318b in
correspondence with the plurality of light source units 104a and
104b. In addition, the power source unit 100 further includes light
source side switches 212a and 212b corresponding to the plurality
of light source units 104a and 104b. The light source side switches
212 connect a switching regulator 102 to the corresponding light
source unit 104 when being turned on.
[0063] An output controlling unit 108 further includes a selection
controlling unit 416. The selection controlling unit 416
sequentially selects each of the plurality of light source units
104a and 104b, and turns on the light source side switch 212
corresponding to the selected light source unit 104. In this
example, a time changing unit 414 sequentially selects the
subsequent light source unit 104 whenever an output controlling
switch 312 is turned off in synchronization with an operation of
the output controlling switch 312. In this case, a secondary coil
404 supplies electric power to the light source unit 104 selected
by the selection controlling unit 416. In this way, the power
source unit 100 sequentially supplies electric power to each of the
plurality of light source units 104a and 104b.
[0064] Here, in this example, a time memorizing unit 412 memorizes
a plurality of OFF time that is respectively corresponding to each
of the plurality of light source units 104a and 104b. A switch
controlling unit 410 switches the output controlling switch 312 on
and off based on the OFF time corresponding to the light source
unit 104 selected by the selection controlling unit 416. In this
case, the time changing unit 414 also changes the OFF time
corresponding to the light source unit 104 selected by the
selection controlling unit 416 based on the output of the end
detecting unit 106. For that purpose, according to this example,
although electric power is sequentially supplied to the plurality
of light source units 104a and 104b, the switching regulator 102
can be controlled adequately. In addition, in this example, a
switch controlling unit 410 computes ON time for which the output
controlling switch 312 should be kept on based on the output
voltage of the secondary coil 404.
[0065] Although the present invention has been described by way of
an exemplary embodiment, it should be understood that those skilled
in the art might make many changes and substitutions without
departing from the spirit and the scope of the present invention.
It is obvious from the definition of the appended claims that
embodiments with such modifications also belong to the scope of the
present invention.
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